Enhanced oil recovery (EOR) is a process of obtaining stranded oil not recoverable from a hydrocarbon production zone using standard extraction processes. EOR is practiced by injecting EOR “flood fluid” under pressure and recovering mobilized oil mixed with the flood fluid. Various flood fluids ere used, including hot water or steam; gases (e.g., nitrogen, carbon dioxide, natural gas, liquid natural gas or propane), solvents (e.g. diesel fuel or other carbonaceous solvents) chemical solutions (e.g., alkaline compounds, polymers and/or surfactants), and low-salinity water.
EOR was first practiced in heavy oil deposits by injecting steam into a wellbore for a long period of time and then recovering mobilized heavy oil from the wellbore. EOR is now widely practiced using one or more injection bores in conjunction with one or more adjacent recovery wells where stranded oil and/or gas are produced to the surface. More recently, EOR has been practiced in a single lateral wellbore in deep tight oil reservoirs. A first pipe is used to inject flood fluid into fractured injection zones and a second pipe in the same wellbore is used to produce stranded oil from fractured production zones interleaved with the injection zones. Packers isolate the injection zones from the interleaved production zones of the wellbore.
While the traditional EOR practices are effective for stranded oil recovery, they are most economical for shallow production zones and relatively short lateral bores When a production zone is deep (i.e., 10,000 feet or more), drilling multiple bores for EOR can become uneconomical. Likewise, when surface access to the reservoir is limited (i.e. near cities, suburban areas, farm land, or wetland) drilling multiple spaced-apart bores within a large area may not be an option. Recent developments in EOR methods for deep, tight oil appear to be suitable for use only in relatively short lateral bores.
There therefore exists a need for a novel method of enhanced oil recovery from lateral wellbores.